WO2016045920A1 - Method for operating a circuit assembly - Google Patents

Abstract

The invention relates to a method for operating a circuit assembly (2) having at least three control stages (8a, 8b, 8c) for at least three phases (u, v, w), wherein each of the control stages (8a, 8b, 8c) has a high-side switch (10a, 10b, 10c) and a low-side switch (12a, 12b, 12c), wherein each high-side switch (10a, 10b, 10c) and low-side switch (12a, 12b, 12c) can be brought into an electrically conductive state and an electrically non-conductive state, wherein a variable influencing the temperature of the high-side switch (10a, 10b, 10c) and/or the low-side switch (12a, 12b, 12c) is determined, either the high-side switch (10a, 10b, 10c) or the low-side switch (12a, 12b, 12c) is selected in groups depending on the variable influencing the temperature, and the selected high-side switch (10a, 10b, 10c) or low-side switch (12a, 12b, 12c) is actuated in a freewheel phase in such a way that the selected high-side switch (10a, 10b, 10c) or low-side switch (12a, 12b, 12c) forms a freewheel during the freewheel phase.

Description

 Description title

 Method for operating a circuit arrangement

The present invention relates to a method for operating a circuit arrangement as well as a computing unit and a computer program for its implementation.

State of the art

BLDC motors (BrushLessDC motors, also called brushless DC motors) have a particularly simple structure. Unlike conventional electric motors, BLDC motors have no mechanical commutator.

A magnetic rotating field for operating the BLDC motor can be generated by means of an inverter whose semiconductor switching elements can be controlled in various ways for this purpose. The drive can e.g. by means of pulse width modulation (PWM), in block mode, by means of space vector, triangular-rectangular, triangular-sine or flat-top modulation.

According to DE 10 2012 210 658 A1, a magnetic rotating field can be provided by means of space vector modulation by means of a circuit arrangement designed as an inverter. The inverter has a control stage for each phase, each with a highside and a lowside switch. Depending on the angular position of the permanent magnet rotor of the BLDC motor, the high side and low side switches of the drive stages are alternately driven to set the magnetic rotating field. The power with which the BLDC motor can operate depends on the power loss of the inverter. The power dissipation causes the inverter to heat up, which limits the maximum power of the BLDC motor. Therefore, there is a need to increase the power that can be delivered by such circuitry.

DISCLOSURE OF THE INVENTION According to the invention, a method for operating a circuit arrangement as well as a computer unit and a computer program for carrying it out with the features of the independent patent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

A circuit arrangement having at least three control stages for at least three phases, e.g. used for a three-phase BLDC motor. Each of the control stages has a high-side switch and a low-side switch, wherein each of the high-side switches and the low-side switch can be brought into an electrically conductive state and into an electrically non-conductive state. It is then determined in a first step, the temperature of the high-side switch and / or the lowside switch influencing size. In a further step, the highside switches or the lowside switch are selected in groups depending on the particular size. In a further step, the selected high-side switches or low-side switches are driven in a freewheeling phase in such a way that the selected high-side switches or low-side switches form a freewheel during the freewheeling phase.

In this case, the group-wise selection of the high-side switches or the low-side switches means that either all high-side switches or all

Lowside switches are selected and that all selected switches are supplied with the same drive signals. Thus, during the freewheeling phases, only the high-side switches or only the low-side switches are loaded according to their temperature and thus heated. Therefore, the circuit heats up more slowly during the freewheeling phases, so that more energy can be supplied to the controlled component, eg a BLDC motor. Furthermore, the circuit arrangement can be dimensioned smaller while maintaining the power of the driven component, which the space requirement for the circuit arrangement and the cost of the

Circuit arrangement reduced.

According to one embodiment, during the freewheel phase, the selected high side switches or lowside switches that form the freewheel are in the conducting state and the other high side switches or lowside switches

Switches are in the non-conductive state. Thus, during the freewheel phase, only the selected highside switches or lowside switches are loaded and thus heated. This makes it possible, in particular, to cool a group of switches more strongly and to use them preferably for freewheeling. Therefore, improved heat dissipation, e.g. a heat sink or larger heat sink, the selected switch more energy is supplied to the selected component, while the other switches do not require such improved heat dissipation. According to another embodiment, in which the temperature of the

Highside switch and / or the Lowside switch influencing size of a power loss, a current, a current level, a current duration and / or a temperature determined itself. Thus, the warming is detected immediately. This simplifies the temperature measurement evaluation.

According to a further embodiment, in the group-wise selection, the quantity is compared with a temperature limit value and, when the temperature limit value is exceeded, the high-side switch or low-side switch which does not exceed the temperature limit value is selected. This ensures in an easy way that the currently selected highside switches or lowside switches will not overheat and be damaged during the freewheeling phases. In accordance with another embodiment, the size of the highside switches and the lowside switches are determined and the highside or lowside switches of the smaller size are selected. By determining the size distribution, different thermal load limits and / or different good cooling connections of the high-side switch or

Lowside switches are considered in the selection. Thus, the individual load limits of the high-side switches and lowside switches can be optimally utilized in order to maximize the maximum power of the driven component.

According to a further embodiment, a semiconductor device, in particular an IC, is used, on which the high-side switches and the low-side switches are arranged, the high-side switches in a middle section of the semiconductor device and the low-side switches in an edge section of the semiconductor device are arranged. By virtue of this arrangement on the semiconductor component, the high-side switches have a better cooling connection than the low-side switches on the semiconductor component. In this case, the semiconductor component can be constructed on a semiconductor substrate with the high-side switches and the low-side switch, or the semiconductor component has a carrier on which several semiconductors are mounted, which form the high-side switches and the low-side switches. The invention can optimize the cooling in such a bridge IC. A bridge IC often has a p-channel transistor as a high-side switch and an n-channel transistor as a low-side switch. The p-channel transistor requires a larger area than the n-channel transistor with the same performance characteristics. Also, the highside switches are usually placed in the middle of the IC and the lowside switches on the edge. The larger area and central positioning allow the highside switches to be better cooled. As a result, the bridge is limited by the poorer cooling connection of the low-side switches, although the high-side switch could additionally process power.

The invention is particularly suitable for use in vehicles, since there harsh environmental conditions prevail with locally critical cooling properties. Preferred applications include the control of electrical Machines in start-stop systems, electric turbochargers and starters, steering systems and gearboxes as well as air conditioning compressors and fans.

An arithmetic unit according to the invention, e.g. a control device of a motor vehicle is, in particular programmatically, configured to perform a method according to the invention.

The implementation of the method in the form of software is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and therefore exists anyway. Suitable data carriers for providing the computer program are, in particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawings

Figure 1 shows a circuit arrangement for driving a three-phase BLDC motor with three phases.

FIG. 2 shows the arrangement of high-side switches and the low-side switches on a semiconductor component for controlling the three-phase BLDC motor. Figure 3 shows a time profile of the drive signals, the duty cycles and the electrical currents of the three phases according to a conventional triangular-sine modulation.

Figure 4 shows a time profile of the drive signals, the duty cycles and the electrical currents of the three phases according to a preferred embodiment of the invention.

Embodiment (s) of the invention

FIG. 1 shows a circuit arrangement 2 for controlling a BLDC motor 4 as a controlled component, the circuit arrangement 2 being fed by an electrical DC voltage source 6.

In the present exemplary embodiment, the BLCD motor 4 has a rotor with one or more permanent magnets and a stator with three

Stator windings, which are assigned to the three phases u, v, w. In order to load each of the stator windings, the circuit arrangement 2 has one, that is to say a total of three drive stages 8a, 8b, 8c.

Thus, the circuit arrangement 2 is formed in the present embodiment as a B6-bridge inverter. Preferred applications of a B6 bridge inverter for driving a BLDC motor 4 in a motor vehicle are e.g. Start-stop systems, electric turbochargers and starters, steering systems and transmissions as well as air conditioning compressors and fans.

Each of the three drive stages 8a, 8b, 8c has a respective high-side switch 10a, 10b, 10c and a low-side switch 12a, 12b, 12c. Furthermore, everyone is

Highside switch 10a, 10b, 10c and low-side switches 12a, 12b, 12c each associated with a freewheeling diode 22a, 22b, 22c, 24a, 24b, 24c. In the present exemplary embodiment, the high-side switches 10a, 10b, 10c are p-channel semiconductor switching elements, such as p-channel transistors, and the lowside switches. Switches 12a, 12b, 12c are n-channel semiconductor switching elements, such as n-channel transistors. Instead of transistors, it is also possible to use p-channel or n-channel power MOSFETs or thyristors, such as GTOs. Via control lines, each of the highside switches 10a, 10b, 10c and each of the

Lowside switch 12a, 12b, 12c connected to a controller 14 of the circuit 2 to the high-side switch 10a, 10b, 10c and the lowside switches 12a, 12b, 12c in an electrically conductive state and in an electrically non-conductive state bring to. For this purpose-as will be explained later-the control unit 14 generates pulse-width-modulated drive signals which switch from the electrically conductive to the non-conductive state and vice versa the highside switches 10a, 10b, 10c and the low-side switch 12a. 12b, 12c effect. The controller 14 may be part of a computing unit, e.g. a control unit of a motor vehicle, be. The controller 14 may include hardware and / or software components.

FIG. 2 shows a preferred arrangement of the high-side switches 10a, 10b, 10c and the low-side switches 12a, 12b, 12c on a semiconductor component 16 (integrated circuit, IC) of the circuit arrangement 2.

The semiconductor device 16 may be constructed on a semiconductor substrate with the high-side switches 10a, 10b, 10c and the low-side switches 12a, 12b, 12c, or the semiconductor device 16 has a carrier on which a plurality of semiconductors are mounted, which are the highside Switch 10a, 10b, 10c and the lowside switches 12a, 12b, 12c form.

It can be seen from FIG. 2 that the high-side switches 10a, 10b, 10c are arranged in a middle section 18 of the semiconductor component 16 and the low-side switches 12a, 12b, 12c are arranged in an edge section 20 of the semiconductor component 16. Due to this arrangement on the semiconductor chip 16, the high-side

Switch 10a, 10b, 10c a better cooling connection than the low-side switches 12a, 12b, 12c to the semiconductor device 16 on. Furthermore, the high-side switches 10a, 10b, 10c designed as p-channel semiconductor switching elements have a larger area than the low-side switches 12a, 12b, 12c designed as n-channel semiconductor switching elements. That's how it is

Heat dissipation of the highside switch 10a, 10b, 10c again improved.

The method for operating a circuit arrangement 2 will now be explained with additional reference to FIGS. 3 and 4. In FIGS. 3 and 4, three pulse-width-modulated drive signals PWM1, PWM2, PWM3 for each of the drive stages 8a, 8b, 8c, including the associated duty cycles T1, T2 and T3, and below those in the three phases u, v, w are shown at the top flowing

Currents i _u , i _v , i _w represented.

In operation, the controller 14 generates the pulse width modulated drive signals PWM1, PWM2, PWM3 for each of the drive stages 8a, 8b, 8c so that the electrical phase currents i _u , i _v , i _w in the BLDC motor 4 generate a rotating magnetic field of desired frequency Drive the rotor form. For example, the drive takes place according to a triangular sine-wave modulation (FIG. 3). In principle, the drive can take place in accordance with an arbitrary drive scheme (eg space vector, triangular fundamental, etc.) as long as the following three drive phases can be identified therein.

Phase 1: All control stages 8a, 8b, 8c have active low-side switches (freewheeling) Phase 2: Not all control stages 8a, 8b, 8c have the same switch position Phase 3: All control stages 8a, 8b, 8c have active high-side switches (freewheeling )

In Phase 1 and Phase 3, no new energy is fed into the engine. The energy in the engine is reduced by a freewheel on all switches. The two phases are functionally identical, which eliminates one of the two phases. The omitted phase is replaced by the other phase. It is important that the phase 2 (different switch position) in their temporal

Process remains unchanged.

The replacement of the phase 1 by the phase 3 and vice versa in Figure 4 leads to a circuit diagram according to Figure 4, which has Fiat top portions. For this In a first step, the temperature and / or power dissipation of the high-side switches 10a, 10b, 10c and / or the low-side switches 12a, 12b, 12c are determined as the variable influencing the temperature of the high-side switches and / or the low-side switches , For this purpose, for example, the temperature of the high-side switch 10a, 10b, 10c and / or the low-side switch 12a, 12b, 12c can be measured and evaluated. Alternatively, an electrical quantity of the high-side switches 10a, 10b, 10c and / or the low-side switches 12a, 12b, 12c may be measured and evaluated. The electrical quantity may be one provided by the high-side switches 10a, 10b, 10c and or the low-side switch 12a, 12b, 12c flowing electric current, one at the high-side switches 10a,

10b, 10c, and / or lowside switches 12a, 12b, 12c, or for a period of time that the highside switches and / or lowside switches are in the electrically conductive state. The duration may e.g. be determined by evaluating a duty cycle of the drive signals PWM1, PWM2, PWM3.

In a second step, the high-side switches 10a, 10b, 10c or the low-side switches 12a, 12b, 12c are selected in groups. For the group-wise selection of the high-side switches 10a, 10b, 10c or the low-side switches 12a, 12b, 12c, the determined temperature is compared with a temperature limit value. If the limit value is exceeded, the high-side switches 10a, 10b, 10c or low-side switches 12a, 12b, 12c which do not exceed the limit value are selected. Alternatively or additionally, it may be provided to select the high-side switches 10a, 10b, 10c or low-side switches 12a, 12b, 12c with the lower temperature. In the present embodiment, the high-side switches 10a, 10b, 10c are selected in groups and - as will be explained - acted upon by the same drive signals.

In a further step, during the freewheeling phase, the highside switches 10a, 10b, 10c and the low-side switches 12a, 12b, 12c are controlled by the control unit 14 by providing the pulse-width-modulated drive signals PWM1, PWM2, PWM3 such that, for example, all highside Switches 10a, 10b, 10c are in the conducting state and all lowside switches 12a, 12b, 12c are in the non-conducting state and all the highside switches 10a, 10b, 10c are so form a freewheel for reducing the electrical or magnetic energy stored in the stator windings.

In a further step, during the power supply phase, the high-side switches 10a, 10b, 10c and the low-side switches 12a, 12b, 12c are controlled by the control unit 14 by providing the pulse-width-modulated drive signals PWM1, PWM2, PWM3 such that they do not all high-side switches 10a, 10b, 10c or that not all lowside switches 12a, 12b, 12c have the same states.

In a further step, during the following freewheeling phase between two power supply phases, the high-side switches 10a, 10b, 10c and the low-side switches 12a, 12b, 12c of the control unit 14 by providing the pulse width modulated drive signals PWM1, PWM2, PWM3 such For example, again all the highside switches 10a, 10b, 10c in the conducting state and all the low side switches 12a, 12b, 12c are in the non-conducting state and thus again all the highside switches 10a, 10b, 10c form the freewheel , Thus, during the freewheeling phases, only the highside switches 10a, 10b,

Loaded 10c and thus heated, which have a better cooling connection compared to the low-side switches 12a, 12b, 12c. Thus, the circuit arrangement 2 heats up more slowly during the freewheeling phases as a result of the described operation, so that more energy can be supplied to the BLDC motor 4. Furthermore, while maintaining the engine power of the BLDC motor 4, the

Circuit arrangement 2 are dimensioned smaller, which reduces the space requirement for the circuit arrangement and the cost of the circuit arrangement 2. If the loads on the high-side switches 10a, 10b, 10c have overheated and this was determined by determining the temperature of the high-side switches 10a, 10b, 10c and / or the low-side switches 12a, 12b, 12c, can the controller 14 by providing the

pulse width modulated drive signals PWM1, PWM2, PWM3 now the Lowside- Switch 12a, 12b, 12c in such a further freewheeling phase drives such that now the low-side switches 12a, 12b, 12c during the further freewheeling phases are in the conductive state.

Thus, a load change takes place from the high-side switches 10a, 10b, 10c to the low-side switches 12a, 12b, 12c during this further freewheeling phase.

Thus, the circuit arrangement 2 is heated even slower by the described operation with these freewheeling phases, so that even more energy can be supplied to the BLDC motor 4 or the circuit arrangement 2 can be dimensioned even smaller while the motor power of the BLDC motor 4 remains the same.

Claims

claims 1 . Method for operating a circuit arrangement (2) having at least three control stages (8a, 8b, 8c) for at least three phases (u, v, w), each of the control stages (8a, 8b, 8c) having a high-side switch (10a, 10b , 10c) and a lowside switch (12a, 12b, 12c), each of the highside switches (10a, 10b, 10c) and the low-side switch (12a, 12b, 12c) in an electrically conductive state and in an electrically non-conductive state can be brought, with the steps:  Determining a variable influencing the temperature of the high-side switches (10a, 10b, 10c) and / or the low-side switches (12a, 12b, 12c),  selecting one of the high-side switches (10a, 10b, 10c) or the low-side switches (12a, 12b, 12c) as a function of the quantity influencing the temperature, and  Driving the selected highside switches (10a, 10b, 10c) or lowside switches (12a, 12b, 12c) in a freewheeling phase such that the selected highside switches (10a, 10b, 10c) or low side switches (12a , 12b, 12c) form a freewheel during the freewheeling phase. 2. The method according to claim 1, wherein during the freewheeling phase the selected high-side switches (10a, 10b, 10c) or lowside switches (12a, 12b, 12c) that form the freewheel, are in the conducting state, and the other highside switches (10a, 10b, 10c) or lowside switches (12a, 12b, 12c) are in the non-conducting state. 3. Method according to claim 1, wherein a power loss, a current and / or a temperature of the high-side switches (10a, 10b, 10c) and / or the low-side switches (12a, 12b, 12c) is determined. Method according to one of the preceding claims, in which, when selecting in groups, the temperature influencing variable is compared with a temperature limit value, and when the temperature limit value is exceeded, the highside switch (10a, 10b, 10c) or lowside switch not exceeding the temperature limit value is selected. Switch (12a, 12b, 12c) are selected. Method according to one of the preceding claims, in which the temperature-influencing size of the high-side switches (10a, 10b, 10c) and the low-side switches (12a, 12b, 12c) is determined and the high-side switches (10a, 10b, 10c ) or lowside switches (12a, 12b, 12c) having the smaller size affecting the temperature. Method according to one of the preceding claims, wherein a semiconductor device (16) is used, on which the high-side switches (10a, 10b, 10c) and the low-side switches (12a, 12b, 12c) are arranged, the high-side switches (16) 10a, 10b, 10c) are arranged in a middle section (18) of the semiconductor device and the low-side switches (12a, 12b, 12c) are arranged in an edge section (20) of the semiconductor device (16). Arithmetic unit which is adapted to carry out a method according to one of the preceding claims. A computer program that causes a computing unit to perform a method according to any one of claims 1 to 6 when executed on the computing unit. Machine-readable storage medium with a computer program stored thereon according to claim 8.